1. Field of the Invention
The present invention relates to couplings or clamps for joining pipes and, more particularly, to clamps for rigidly securing grooved pipes end to end.
2. Description of Prior Art
For years, two part clamps have been used for securing the ends of pipes to one another. These clamps are generally two part clamps wherein each part engages half of the circumference of the joined pipes. The pipes are formed with annular grooves for receiving internally oriented ridges of the clamp halves. A circular gasket bridges the joined pipe ends and is retained in place by the clamp to seal the pipe junction. Longitudinally oriented separation between the abutting pipes is generally prevented by the interference fit resulting from the ridges of the clamp engaging the grooves in the pipes. Rotational displacement of the pipes about the longitudinal axis is generally prevented by and a function of the clamping force and friction between the clamp and the pipe ends. The two clamp halves are secured to one another by a pair of diametrically opposed bolts and nuts penetrably engaging mating bolting pads extending laterally from the respective clamp halves. The clamps may be manufactured to clamp specifically sized pipes having specifically sized depth of grooves; with these known factors, the bolting pads can be configured to be adjacent one another when the clamp is secured in place. Thereby, the clamp will represent a continuous ring about the ends of the pipes to substantially immobilize them and eliminate all gaps between the clamp and the encircled pipe ends. Unfortunately, the pipe ends are sometimes undersize or oversize. Additionally, the depth of the pipe grooves may be more or less than standard. Under such circumstances, the bolting pads may be drawn adjacent one another by nut and bolt means and make contact before the encircled ends of the pipes are securely clamped therebetween. The resulting fit will be too loose to immobilize the pipe ends. Alternatively, the bolting pads may not be capable of being drawn adjacent one another by the nut and bolt means due to oversize of the ends of the pipes or due to lack of sufficient depth within the grooves at the pipe ends. The resulting gap between the bolting pads will provide a source for movement between the clamp halves as a result of forces imposed by the joined pipes. This situation may cause a hazard and is generally considered unsatisfactory.
A presently employed solution for accommodating variances in the ends of pipes to be joined and the grooves formed therein is that of setting the abutting surfaces of the bolting pads at an angle. Necessarily, the holes through which the bolt and nut means extend must be elongated to accommodate movement of the respective clamp halves along the longitudinal axis of the joined pipes. On drawing the bolting pads toward one another, they Will slide in contact with one another until further tightening ceases. This configuration has the benefit of permitting the clamp halves to be drawn toward one another until a tight fit with the joined ends of the pipes is achieved. However, the clamp halves will not be located in a common plane and asymmetrical loading upon the ends of the pipes may occur. Moreover, the sliding movement of the clamp halves during tightening may have detrimental effects upon the integrity and seal of the circular gasket bridging the joined ends of the pipes.
Clamps of the type described above rely upon a tight fit and friction to immobilize the joined pipes with one another. Because the friction is a function of the torque applied to the bolt and nut means drawing the two clamps halves toward one another, non uniformity between installed clamps may result. Torsional forces imposed between the joined pipes may be sufficient to overcome the friction imposed by the clamp and rotation of one pipe with respect to the other may result. Such rotation may cause stresses or strains upon other segments of the pipe network and failure may occur.
Numerous examples of clamps falling within the above enumerated categories exist and have existed for decades. Various modifications of configuration of the bolting pads are known. Moreover, various configurations of and materials used for the gasket retained in place by the clamp are well known.
The present invention was developed particularly for the purpose of preventing rotation of one pipe about its longitudinal axis with respect to a joined pipe. To obtain these results, a plurality of teeth are formed in each clamp half adjacent each of the opposed spaced apart pair of ridges. On tightening of the clamp about the joined ends of the pipes, the teeth interfere with and penetrably engage the anterior side wall of the groove in the encircled pipe. The resulting physical or mechanical interconnection operates in the manner of a key and keyway to prevent rotation of each pipe end with the encircling clamp. Accordingly, the resulting mechanical lock, in addition to friction, Will tend to discourage rotational motion between the joined pipes and about the longitudinal axis. For reasons not presently known, the interference fit between the teeth and the side Walls of the grooves tends to preclude displacement of the joined pipes along the longitudinal axis in response to high pressures wi thin the pipes. To accommodate for differences in pipe diameters and groove depth, a tongue and groove structure is employed in conjunction with the bolting pads to prevent gaps about the engaged pipes even though the bolting pads may not be drawable adjacent one another.
It is therefore a primary object of the present invention to provide a clamp for physically interlocking with the joined ends of apair of encircled pipes to prevent rotation between the pipes about their common longitudinal axis.
Another object of the present invention is to provide an interference fit about the longitudinal axis between a clamp on a pipe encircled by the clamp.
Yet another object of the present invention is to provide a clamp for mechanically interlocking with encircled pipes.
Yet another object of the present invention is to provide a plurality of teeth interior of a clamp for engaging a side wall of a groove in an encircled pipe.
Still another object of the present invention is to provide a plurality of teeth interior of a clamp for engaging a side wall of a groove formed in each end of a pair of joined pipes.
A further object of the present invention is to provide teeth on the interior surface of the ridge of a clamp for penetrably engaging the side wall of a groove of an encircled pipe.
A yet further object of the present invention is to provide a tongue and groove apparatus for avoiding a gap between bolting pads of a pipe clamp.
Still another object of the present invention is to provide a method for mechanically interlocking and frictionally engaging joined pipe ends with a clamp.
These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.